Nuclei for use in solvent transfer systems



United States Patent US. C]. 96-29 34 Claims ABSTRACT OF THE DISCLOSURE Silver precipitation nuclei for diffusion transfer development are obtained by mixing a metallic selenide or sulfide with a more soluble silver salt. The metal is nickel, copper, iron, cobalt or Groups II-B and IVB of the Periodic Table.

' This invention concerns nuclei and the preparation of nuclei for use in photographic solvent transfer systems.

The solvent transfer or diffusion transfer system as described in Rott US. Pat. 2,352,014 is a photographic process in which an exposed silver halide emulsion is developed in the presence of a silver halide solvent and contacted against a receiving support having thereon silver precipitating nuclei. The soluble silver halide diffuses imagewise from the undeveloped areas of the silver halide emulsion to the nuclei where silver is precipitated to form a positive image.

Various substances have been disclosed in the art for use as silver precipitating agents in the diffusion transfer process including metals such as colloidal silver, salts of metals or metalloids such as silver sulfide, nickel sulfide, and the like. However, it has been desirable to produce solvent transfer images having higher maximum density, more neutral tone, improved tonal reproduction, longer stability, etc., than produced by the previously described nuclei.

Metal sulfide or selenide nuclei have been found to be particularly suitable for use in the diffusion transfer process when prepared in very fine particle size. However, it has been customary for these nuclei to be prepared fresh prior to coating, since they have often had poor stability on standing. For instance, when a dispersion of the nuclei was permitted to stand, the dispersion would appear to lose density, possibly due to a bleaching effect, so that the nuclei would no longer be of practical use.

I have found that nuclei obtained by mixing a metal (other than silver) sulfide or selenide with a silver salt possess improved photographic qualities over nuclei previously known in the art when used in the diffusion transfer system.

One object of this invention is to provide improved nuclei for use in the diffusion transfer system. Another object is to provide nuclei which result in higher maximum density, more neutral tones, improved tonal reproduction, and longer stability over previously known nuclei. A further object is to provide a process of making nuclei for use in the diffusion transfer system. An additional object is to provide nuclei by blending a metal sulfide or selenide and a silver salt to provide a synergistic effect.

The above objects are attained by blending a metal sulfide or selenide (with the exception of these containing a silver cation) and a silver salt in a molar ratio of silver salt to metal sulfide or selenide of about 1:20 to 5:1, with particularly good results being obtained between about 1:10 and 1:1. In a preferred embodiment, the nuclei have an average particle size of from about 7 A. to 2,500 A.

When nickel sulfide nuclei are to be precipitated, a particularly suitable method is to prepare a dilute gelatin solution or similar colloid solution in which one of the 3,532,497 Patented Oct. 6, 1970 reactants is then dissolved, such as sodium sulfide. A solution of nickelous nitrate is then dumped into the mixture and activated rapidly to provide a rapid reaction between the two reactants and to prepare finely-divided nuclei. Silver iodide can then be precipitated in a similar manner by mixing aqueous potassium iodide and silver nitrate solution. The silver iodide can then be mixed with the nickelous sulfide.

Other metal sulfides or selenides which can be used are those of nickel, copper, iron, cobalt and the metals of groups II-B and IV-B of the Periodic Table, e.g., cadmium, zinc, cobalt, lead, and the like. The silver salts which can be used include silver iodide, silver bromide, silver chloride, silver nitrate, p-toluenesulfonic acid silver salt, etc., provided the silver salt is more soluble in an aqueous hydrophilic colloid emulsion than the metal sulfide or selenide. Both the silver salt and the metal sulfide or selenide will, of course, be more water-soluble than silver sulfide or silver selenide.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 Nickel sulfide nuclei are produced by adding 19 ccs. of 1.0 N sodium sulfide to a precipitation vessel containing 50 grams of 10 percent gelatin solution and 1435 ccs. of water at a pH of about 5.7 and a temperature of about 104 F. About 5 seconds after the addition of the sodium sulfide solution, a solution containing 20.8 ccs. of 1.0 N nickelous nitrate and 535 ccs. of water is dumped into the reaction mixture over a period of 10 seconds with rapid mechanical agitation. At the end of the addition, the nuclei are stirred for 30 seconds at 104 F. Four hundred fifty grams of a 10 percent gelatin solution are then added and the nuclei stirred at 104 F. for an additional 15 minutes.

EXAMPLE 2 Silver iodide nuclei are prepared as in Example 1 by substituting potassium iodide for sodium sulfide and substituting silver nitrate for nickelous nitrate.

A receiving sheet is prepared as follows:

A dispersion is prepared with 500 grams of the nickel sulfide nuclei dispersion of Example 1, 100 grams of the silver iodide nuclei dispersion of Example 2, 380 grams of a 10 percent gelatin solution and 1783 ccs. distilled water. To this dispersion, while stirring at 104 F., are added 30 ccs. as a 1 percent solution in methanol of 1- methyl-1,2,3,6-tetrahydro-1,3,5-triazine-4-thiol, 60 ccs. as a 1 percent solution in methanol of 3-mercapto-1,2,4- triazole, and 44 ccs. as a 10 percent solution in distilled water of 3,8-dithiodecane-1,10-bis-(N-methyl piperidinium-p-toluene sulfonate). To this added a coating aid and ccs. of a 10 percent formaldehyde solution as a hardener. The dispersion is then coated on white pigmented cellulose acetate at a coverage to yield 82.5 mg. gelatin per square foot.

A silver bromoiodide emulsion is coated on a white pigmented cellulose acetate support at a coverage to yield 59.3 mg. silver and 550 mg. gelatin per square foot. A gelatin overcoat is applied over this layer at a coverage to yield 146 mg. gelatin per square foot.

This negative element is exposed to light of daylight quality in an intensity scale sensitometer containing an 0.6 neutral density filter for 0.1 second. After exposure, the negative is soaked for 6 seconds in the following developer solution.

DEVELOPER 1-Phenyl-4-methyl pyrazolidone-1.5 g.

KOH (45% cc.

Sodium isoascorbateg.

Sodium thiosulfate pentahydrate-JS g.

KI (0.1% cc.

KBr-2 g.

Tetra decyloxy pentaethoxy ethyl sulfate, NHA,

salt30 cc.

H O to 1000 cc.

pH adjusted to 10.5 with H 80 (50% soln.)

The negative is then immediately brought in contact with the receiver sheet of Example 3. After 2 minutes, the negative element is separated from the receiver sheet to yield a high quality continuous tone black-and-whit'e print on the receiver sheet.

EXAMPLE 5 Dispersions were prepared with nuclei as described in Example 3 as shown in the following table, except that for the control nuclei wherein only the metal sulfide was used without the addition of the silver halide, 500 ccs. of the dispersion prepared as described in Example 1 was used. Nuclei which had been prepared according to Examples 1 and 2, were tested for stability: fresh, after one week incubation, and after four weeks incubation. At the end of these incubation periods, the coating mixtures were prepared as in Example 3 and were tested for photographic properties by coating on a receiving support as described in Example 3 and processed as in Example 4. The resulting densities are shown in the following table.

4 weeks 1 week bulk Fresh, incubated, holding,

Nuclei Du. mux Dmux- NiS 1. 59 1. 28 1. 26 NiS plus AgI- 1. 64 1.42 1. 60 NiS plus AgBr. 1. 76 1. 56 1. NiS plus AgCl 1. 73 1. 43 1. 55 NiS plus AgNO 1.80 1. 50 1. 46 COS 1. 56 1. 27 0. 95 COS plus AgL- 1. 63 1. 44 1. (308 plus AgBr 1.79 1. 47 1. 56 008 plus Ag 1. 75 1. 48 1. 56 008 plus Ag 1. 78 1. 34 1. 59 Zn 0. 26 0. 20 0. 12 ZnS plus AgI 1.16 1.08 1. 34 ZnS plus AgBi 1. 04 1.18 1. 26 ZnS plus AgC 1.17 1.15 1. 30 ZnS plus AgNO 1. 24 1. 14 l. 31 0. 91 1. 14 0. 41 PbS plus AgL. 1.06 1.01 1. 04 PbS plus AgBL. 1.10 1.06 0.86 PbS plus AgCl-. 1. 23 1. 09 1. 00 PbS plus AgNO 0. 97 1.14 0. 75 AgI 0. 25 0. 19 0. 24 A4531--. 0. 03 0. 02 0. 24 AgCl 0. 02 0. 01 0. 17

Various methods are known in the art using the nuclei in a photographic diffusion transfer process. The improved nuclei of this invention can be used in the conventional binders and substrates and in any of the known embodiments of the diffusion transfer process and may be used with the photographic silver halide emulsions known in the art. These nuclei may also be used in layers in conjunction with other components such as those disclosed in the art.

Other noble metals may be used in place of silver such as gold, platinum, etc. Moreover, a mixture may be used of the metal nuclei blended with at least one noble metal salt.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. Silver precipitation nuclei useful in the silver salt diffusion transfer process obtained by admixing in the absence of a silver halide complexing agent 4 (a) at least one salt selected from the class consisting of sulfides and selenides of a metal other than silver, selected from the class consisting of nickel, copper, iron, cobalt and the metals of Groups II-B and IV-B of the Periodic Table with (b) at least one silver salt which is more water soluble than the said metal selenide or metal sulfide.

2. Nuclei of claim 1 which have an average particle size of 7 A. to 2500 A.

3. Nuclei of claim 1 obtained by admixing silver iodide and nickel sulfide.

4. Nuclei of claim 1 in which the metal salt is a sulfide.

5. Nuclei of claim 1 in which the metal salt is a selenide.

6. Nuclei of claim 1 in which the metal salt is an aqueous suspension and the silver salt is an aqueous suspension.

7. Nuclei of claim 1 in which the metal salt is mixed with the silver salt in a molar ratio of 1:10.

8. Nuclei of claim 1 in which the molar ratio of the silver salt to the metal salt is within the range of about 1:20 and 5:1.

9. Nuclei of claim 1 wherein the said silver salt and the said metal salt are admixed in an aqueous medium containing a water permeable, hydrophilic colloid.

10. Nuclei of claim 1 wherein the said silver salt and the said metal salt are admixed in an aqueous medium containing gelatin.

11. A receiving sheet for use in the diffusion transfer photographic process comprising a support having thereon a layer containing the nuclei of claim 1.

. 12. A receiving sheet for use in the diffusion transfer process comprising a paper support having coated thereon a layer containing a water permeable, hydrophilic colloid and nuclei of claim 1.

13. A receiving sheet of claim 12 in which the hydrophilic colloid is gelatin.

14. Silver precipitation nuclei useful in the silver salt diffusion transfer process obtained by admixing (a) at least one salt selected from the class consisting of sulfides and selenides of a metal other than silver, selected from the class consisting of nickel, copper, iron, cobalt and the metals of Groups II-B and IV-B of the Periodic Table with (b) at least one silver salt selected from the class consisting of silver iodide, silver bromide, silver chloride and silver nitrate.

15. Nuclei of claim 14 which have an average particle size of 7 A. to 2500A.

16. Nuclei of claim 14 in which said metal salt is a sulfide.

17. Nuclei of claim 14 in which said metal salt is a selenide.

18. Nuclei of claim 14 in which said metal salt is an aqueous suspension and said silver salt is an aqueous suspension.

19. Nuclei of claim 14 in which said metal salt is mixed with said silver salt in a molar ratio of 1:10.

20. Nuclei of claim 14 in which the molar ratio of said silver salt to said metal salt is within the range of about 1:20 to 5:1.

21. Nuclei of claim 14 wherein said silver salt and said metal salt are admixed in an aqueous medium containing a water permeable, hydrophilic colloid.

22. Nuclei of claim 14 wherein the said silver salt and the said metal salt are admixed in an aqueous medium containing gelatin.

23. A receiving sheet for use in the diffusion transfer photographic process comprising a support having thereon a layer containing the nuclei of claim 14.

24. A receiving sheet for use in the diffusion transfer process comprising a paper support having coated thereon a layer containing a water permeable, hydrophilic colloid and nuclei of claim 14.

25. A receiving sheet of claim 24 in which the hydrophilic colloid is gelatin.

26. In a method of making positive photographic images comprising developing an exposed photographic silver halide element with a photographic silver halide developing solution, dissolving unexposed silver halide in a silver halide solvent, diffusing imagewise the unexposed silver halide from said photographic element in contiguity with silver precipitation nuclei to a receiving surface placed in close contiguity to said silver halide element, the step of employing a receiving sheet having thereon silver precipitation nuclei obtained by admixing, in the absence of a silver halide complexing agent.

(a) at least one salt selected from the class consisting of sulfides and selenides of a metal other than silver, selected from the class consisting of nickel, copper, iron, cobalt and the metals of Groups II-B and IV-B of the Periodic Table and (b) at least one silver salt which is more water soluble than the said metal selenide or metal sulfide.

27. A method according to claim 26 wherein said nuclei are present in a layer coated on the surface of said receiving sheet, said layer comprising in addition to said nuclei, a Water permeable, hydrophilic colloid.

28. A process of claim 26 in which said nuclei have an average particle size of 7 A. to 2500 A.

29. A process of claim 26 in which said nuclei are obtained by admixing silver iodide and nickel sulfide.

30. A process of claim 26 in which said metal salt is a sulfide.

31. A process of claim 26 in which said metal salt is a selenide.

32. A process of claim 26 in which said metal salt is mixed with said silver salt in a molar ratio of 1:10.

33. A process of claim 26 in which the molar ratio of said silver salt to said metal salt is within the range of about 1:20 and 5:1.

34. A process of claim 26 in which said hydrophilic colloid is gelatin.

References Cited OTHER REFERENCES Hodgman, et al.: Handbook of Chemistry and Physics, 1956, pp. 5945.

NORMAN G. TORCHIN, Primary Examiner I. E. CALLAGHAN, Assistant Examiner US. Cl. X.R. 96-76 

